Communication channels through electrically conducting enclosures via frequency selective windows

Abstract

Communication of information between the inside and the outside of an electrically conducting enclosure is performed through the use of a frequency selective surface on the electrically conducting enclosure, which permits passage of electromagnetic waves at particular frequencies, but prohibits waves of other frequencies from penetration. Thus, one or more objects contained within the electrically conducting enclosure, which include radio frequency tags attached to the objects containing information about the objects, may be monitored or interrogated by the transmission of an electromagnetic wave at the permitted frequency through the frequency selective surface. With such a system, control and inventory of enclosed objects may be performed while the EMI shielding function of the electrically conducting enclosure is maintained.

What is claimed is: 
     
       1. A system for providing information about one or more objects within electrically conducting packaging that shields the one or more objects from electromagnetic radiation originating from outside of the packaging without providing such information on an outside surface of the packaging and without requiring the packaging to be opened, comprising: a radio frequency tag carried by at least one object within the electrically conducting packaging for receiving a first electromagnetic wave having a first carrier frequency and automatically radiating a second electromagnetic wave having a second carrier frequency in response thereto, the radio frequency tag carrying information about the object and the second electromagnetic wave being modulated with the information about said object;   a radio frequency transponder outside of the electrically conducting packaging for transmitting the first electromagnetic wave towards the electrically conducting packaging and for receiving the second electromagnetic wave from the electrically conducting packaging; and   a frequency selective surface window in the electrically conducting packaging that permits the first electromagnetic wave to enter the electrically conducting packaging and reach the radio frequency tag and further permits the second electromagnetic wave to exit from the electrically conducting packaging and reach the transponder to thereby communicate the information about the object to the transponder.   
     
     
       2. The system as recited in claim 1, wherein said frequency selective surface window is an aperture that is covered by an electrically conducting coated substrate with periodic patterns of one or more openings that are of a size and have a spacing such that said aperture resonates at said first and second carrier frequencies for one or more wave polarizations. 
     
     
       3. The system as recited in claim 2, wherein said openings have any one or more of the following shapes: patches, crosses, and strips. 
     
     
       4. The system as recited in claim 1, wherein said frequency selective surface window is one or more punched periodic aperture arrays that are put through said electrically conducting packaging, said one or more periodic aperture arrays having openings with a size and a spacing such that said periodic aperture arrays resonate at said first and second carrier frequencies for one or more wave polarizations. 
     
     
       5. The system as recited in claim 1, further comprising a data processing system coupled to said transponder, said data processing system comprising a processor, a storage means, and an input/output means coupled together via a bus, wherein said information communicated to said transponder is transferred to said data processing system via said input/output means. 
     
     
       6. The system as recited in claim 1, wherein said first electromagnetic wave further causes said tag to change a state on a logic circuit on said tag and a further electromagnetic wave interrogates said tag to determine said state of said tag. 
     
     
       7. The system as recited in claim 1, wherein said first and second carrier frequencies are equal. 
     
     
       8. The system as recited in claim 1, wherein said frequency selective surface window is an aperture in said packaging that is covered by an electrically insulating substrate with periodic patterns of one or more dielectric regions that are of a size and have a spacing so that said enclosure aperture resonates at said first and second carrier frequencies for one or more wave polarizations. 
     
     
       9. The system as recited in claim 1, wherein said frequency selective surface window is one or more patterned periodic aperture arrays that are placed in an opening in said electrically conducting packaging, said one or more periodic arrays having dielectric regions with a size and having a spacing so that said periodic arrays resonate at said first and second carrier frequencies for one or more wave polarizations. 
     
     
       10. The system as recited in claim 9 wherein said periodic array dielectric regions have any one or more of the following shapes: patches, crosses, and strips. 
     
     
       11. A system for providing information about an internal part within an electrically conducting enclosure without providing such information on an outside surface of the enclosure and without requiring the enclosure to be opened, comprising: a radio frequency tag carried by at least one internal part within the electrically conducting enclosure for receiving a first electromagnetic wave having a first carrier frequency and automatically radiating a second electromagnetic wave having a second carrier frequency in response thereto, the radio frequency tag carrying information about the internal part and the second electromagnetic wave being modulated with the information about said internal part;   a radio frequency transponder outside of the electrically conducting enclosure for transmitting the first electromagnetic wave towards the electrically conducting enclosure and for receiving the second electromagnetic wave from the electrically conducting enclosure; and   a frequency selective surface window in the electrically conducting enclosure that permits the first electromagnetic wave to enter the electrically conducting enclosure and reach the radio frequency tag and further permits the second electromagnetic wave to exit from the electrically conducting enclosure and reach the transponder to thereby communicate the information about the object to the transponder.   
     
     
       12. The system as recited in claim 11, wherein said frequency selective surface window is an aperture that is covered by an electrically conducting coated substrate with periodic patterns of one or more openings that are of a size and have a spacing such that said aperture resonates at said first and second carrier frequencies for one or more wave polarizations. 
     
     
       13. The system as recited in claim 12, wherein said openings have any one or more of the following shapes: patches, crosses, and strips. 
     
     
       14. The system as recited in claim 11, wherein said frequency selective surface window is one or more patterned periodic aperture arrays that are placed in an opening in said electrically conducting enclosure, said one or more periodic arrays having dielectric regions with a size and having a spacing so that said periodic arrays resonate at said first and second carrier frequencies for one or more wave polarizations. 
     
     
       15. The system as recited in claim 14 wherein said periodic array dielectric regions have any one or more of the following shapes: patches, crosses, and strips. 
     
     
       16. A method for providing information about one or more objects stored within an electrically conducting transport container that shields the one or more objects from electromagnetic radiation originating from outside of the transport container without providing such information on an outside surface of the transport container and without requiring the transport container to be opened, comprising: forming a frequency selective surface window in an electrically conducting transport container that selectively passes first and second carrier frequencies;   attaching a radio frequency tag to at least one object and storing said tagged object within said transport container, said tag carrying information about the object;   interrogating the transport container with a radio frequency transponder located outside of the transport container, said transponder transmitting a first electromagnetic wave having said first carrier frequency towards the frequency selective surface window in the transport container, said surface window permitting the first electromagnetic wave to enter said transport container and reach said tag, said tag receiving said first electromagnetic wave and automatically radiating a second electromagnetic wave having said second carrier frequency in response thereto, said second electromagnetic wave being modulated with the information about said object, said surface window further permitting said second electromagnetic wave to exit said transport container and reach said transponder; and   receiving and demodulating said second electromagnetic wave at said transponder to thereby receive the information about the object at the transponder.   
     
     
       17. The method as recited in claim 16, wherein said frequency selective surface window is an aperture that is covered by a substrate having an electrically conducting coating with periodic patterns of one or more openings that are of a size and have a spacing such that said aperture resonates at said first and second carrier frequencies for one or more wave polarizations. 
     
     
       18. The method as recited in claim 16, wherein said frequency selective surface window has a periodic pattern of one or more patches, crosses, or strips, with the size and spacing thereof adjusted to be resonant at said first and second carrier frequencies for one or more wave polarizations. 
     
     
       19. The method as recited in claim 16, wherein said frequency selective surface window is one or more punched periodic aperture arrays that are put through said electrically conducting transport container, said one or more periodic aperture arrays being of a size and having a spacing such that said periodic aperture arrays resonate at said first and second carrier frequencies for one or more wave polarizations. 
     
     
       20. The method as recited in claim 16, wherein said interrogating step further comprises the steps of transmitting said first electromagnetic wave having said first carrier frequency to cause said tag to change a state on a logic circuit on said tag, and transmitting a further electromagnetic wave having said first carrier frequency to interrogate said tag to determine said state of said tag. 
     
     
       21. The method as recited in claim 16, wherein said first and second carrier frequencies are equal. 
     
     
       22. The method as recited in claim 16, wherein said frequency selective surface window is formed as one or more patterned periodic aperture arrays that are placed in an opening in said electrically conducting transport container, said one or more periodic arrays having dielectric regions with a size and having a spacing so that said periodic arrays resonate at said first and second carrier frequencies for one or more wave polarizations. 
     
     
       23. The method as recited in claim 22 wherein said periodic array dielectric regions have any one or more of the following shapes: patches, crosses, and strips.